The 1,2-benzoisothiazoline-3-one (BIT) has been known as anti-microbially active substance and is used as preservative in technical applications or, in general, as an additive which is suitable to counteract material destruction ("Mikromatz", in german) caused by microbes. To make this compound available in a convenient preparation that can be metered easily, an aqueous dispersion may be prepared with the crude BIT obtained during synthesis. Such dispersions, however, are not stable when stored and will settle in the course of time. GB Patent 11 91 253 has disclosed aqueous solutions of crude BIT with two or more amine compounds of the series comprising the diethanol amine, triethanol amine, diisopropanol amine, triisopropanol amine or morpholine; these aqueous solutions contain BIT in the form of a mixture of the amine salts. Furthermore, GB Patent 13 30 531 has disclosed that BIT amine salts can be imparted with better stability in a cold environment when they are present in the form of solutions in aliphatic, cycloaliphatic or heterocyclic amines having 2 to 6 C atoms and do not have hydroxyl and ether groups. The effectiveness of these preparations against material destruction, however, frequently is not adequate.